An optical fiber having metallic micro/nano-structure on end-facet, and a fabrication method and an application method thereof. The metallic micro/nano-structure is a micro-nano structure resonance cavity on a metallic film, and generates surface plasmon resonance when an optical fiber guided wave is incident. In the fabrication method according to the present invention, the metallic micro/nano-structure on the surface of the substrate is aligned with and is adhered to the end-facet of the optical fiber, and is removed for transferring to the end-facet of the optical fiber. In the application method according to the present invention, the end-facet of the optical fiber is contacted with or moved towards a medium, and a refractive index of the medium is measured by measuring reflection of an optical fiber guided wave by the metallic micro/nano-structure resonance cavity.